Mroboto Any half way decent IMAP client (don't ever set up an email service using POP!!!) will make use of the IMAP protocol's ability to push notifications. As mentioned by @evalda , Fairemail is one such IMAP client. K9mail probably can as well -- they used to be able to, then disabled it "temporarily", and I haven't looked at it since, so I can't say for certain that they re-enabled it.
That isn't to say that the email-to-sms approach is worthless. It has the advantage of not requiring a DATA connection, which makes it really good for situations like ROAMING since data can be absurdly expensive, and most service providers have recognized that charging you for incoming SMS messages is unfair since receiving a message is not something you can control.